1*5e3eaea3SApple OSS Distributions<h2>device_read_async</h2> 2*5e3eaea3SApple OSS Distributions<hr> 3*5e3eaea3SApple OSS Distributions<p> 4*5e3eaea3SApple OSS Distributions<strong>System Trap</strong> - Read a sequence of bytes from a device object. 5*5e3eaea3SApple OSS Distributions<h3>SYNOPSIS</h3> 6*5e3eaea3SApple OSS Distributions<pre> 7*5e3eaea3SApple OSS Distributions<strong>kern_return_t device_read_async</strong> 8*5e3eaea3SApple OSS Distributions <strong>(mach_port_t</strong> <var>device</var>, 9*5e3eaea3SApple OSS Distributions <strong>mach_port_t</strong> <var>queue</var>, 10*5e3eaea3SApple OSS Distributions <strong>mach_port_t</strong> <var>request_id</var>, 11*5e3eaea3SApple OSS Distributions <strong>dev_mode_t</strong> <var>mode</var>, 12*5e3eaea3SApple OSS Distributions <strong>recnum_t</strong> <var>recnum</var>, 13*5e3eaea3SApple OSS Distributions <strong>io_buf_len_t</strong> <var>bytes_wanted</var><strong>);</strong> 14*5e3eaea3SApple OSS Distributions</pre> 15*5e3eaea3SApple OSS Distributions<h3>PARAMETERS</h3> 16*5e3eaea3SApple OSS Distributions<dl> 17*5e3eaea3SApple OSS Distributions<p> 18*5e3eaea3SApple OSS Distributions<dt> <var>device</var> 19*5e3eaea3SApple OSS Distributions<dd> 20*5e3eaea3SApple OSS Distributions[in device send right] A device port to the device to be read. 21*5e3eaea3SApple OSS Distributions<p> 22*5e3eaea3SApple OSS Distributions<dt> <var>queue</var> 23*5e3eaea3SApple OSS Distributions<dd> 24*5e3eaea3SApple OSS Distributions[in io_done queue send right] The port returned from 25*5e3eaea3SApple OSS Distributionsio_done_queue_create. 26*5e3eaea3SApple OSS Distributions<p> 27*5e3eaea3SApple OSS Distributions<dt> <var>request_id</var> 28*5e3eaea3SApple OSS Distributions<dd> 29*5e3eaea3SApple OSS Distributions[in send right] An unique request identifier that will be passed back as 30*5e3eaea3SApple OSS Distributionspart of the io_done_result structure. 31*5e3eaea3SApple OSS Distributions<p> 32*5e3eaea3SApple OSS Distributions<dt> <var>mode</var> 33*5e3eaea3SApple OSS Distributions<dd> 34*5e3eaea3SApple OSS Distributions[in scalar] I/O mode value. Meaningful options are: 35*5e3eaea3SApple OSS Distributions<p> 36*5e3eaea3SApple OSS Distributions <dl> 37*5e3eaea3SApple OSS Distributions<dt> <strong>D_NOWAIT</strong> 38*5e3eaea3SApple OSS Distributions<dd> 39*5e3eaea3SApple OSS DistributionsDo not wait if data is unavailable. 40*5e3eaea3SApple OSS Distributions </dl> 41*5e3eaea3SApple OSS Distributions<p> 42*5e3eaea3SApple OSS Distributions<dt> <var>recnum</var> 43*5e3eaea3SApple OSS Distributions<dd> 44*5e3eaea3SApple OSS Distributions[in scalar] Record number to be read. 45*5e3eaea3SApple OSS Distributions<p> 46*5e3eaea3SApple OSS Distributions<dt> <var>bytes_wanted</var> 47*5e3eaea3SApple OSS Distributions<dd> 48*5e3eaea3SApple OSS Distributions[in scalar] Size of data transfer. 49*5e3eaea3SApple OSS Distributions</dl> 50*5e3eaea3SApple OSS Distributions<h3>DESCRIPTION</h3> 51*5e3eaea3SApple OSS Distributions<p> 52*5e3eaea3SApple OSS DistributionsThe <strong>device_read_async</strong> interface enqueues a read operation for a 53*5e3eaea3SApple OSS Distributionssequence of bytes from a device object. The meaning of recnum as well 54*5e3eaea3SApple OSS Distributionsas the specific operation performed is device dependent. 55*5e3eaea3SApple OSS Distributions<h3>RETURN VALUES</h3> 56*5e3eaea3SApple OSS Distributions<dl> 57*5e3eaea3SApple OSS Distributions<strong>device_read_async</strong> returns only invalid parameter errors. 58*5e3eaea3SApple OSS Distributions<dd> 59*5e3eaea3SApple OSS Distributions</dl> 60*5e3eaea3SApple OSS Distributions<h3>RELATED INFORMATION</h3> 61*5e3eaea3SApple OSS Distributions<p> 62*5e3eaea3SApple OSS DistributionsFunctions: 63*5e3eaea3SApple OSS Distributions<a href="device_read_async_inband.html"><strong>device_read_async_inband</strong></a>, 64*5e3eaea3SApple OSS Distributions<a href="DR_overwrite_async.html"><strong>device_read_overwrite_async</strong></a>, 65*5e3eaea3SApple OSS Distributions<a href="device_write_async.html"><strong>device_write_async</strong></a>, 66*5e3eaea3SApple OSS Distributions<a href="device_write_async_inband.html"><strong>device_write_async_inband</strong></a>, 67*5e3eaea3SApple OSS Distributions<a href="io_done_queue_create.html"><strong>io_done_queue_create</strong></a>. 68